How to change the background of the text area in Bluefish? Go to the Fonts & Colors section of preferences and select what you want, you may say, and I’m sure that works almost every time. In my case, I decided to try out Bluefish and wanted a dark color scheme as it’s easier on the eyes for me that way. I went into the preferences and set up a nice color scheme, applied it and found that all the changes I had made were applied except for the background color. The eventual remedy was to go into Appearances (Ubuntu Mate menu) and select a default theme, rather than the custom theme I had been using. This immediately resolved the issue. Interestingly, there is a Use system wide color settings option in Bluefish which I had already tried both on and off to no effect. This is presumably some sort of gtk glitch, and certainly not the end of the world, but if it happens to you, maybe this post will save you some time.
EDIT
My bad, I misinterpreted what happened. The theme I randomly switched to just happened to have a background color setting very close to what I was trying to use. It turns out that Bluefish is still using the background color from the theme and not the custom color I’m defining in the preferences. In any case, I have since discovered the awesomeness that is Kate. I see no reason to look further.